The first time really was an accident. His body had moved on its own before his mind had a chance to catch up. It had been after Midoriya's match against Todoroki at the sports festival. Sadness practically radiated from the boy, terrified that he had disappointed his mentor and idol, but the determination was still there that he had done what he felt was right and he would not apologise for it. Little did he know, Toshinori was already convinced that this particular young man could never disappoint him. He could search the Earth and never find anyone better. Izuku Midoriya was perfect. As a successor, of course, he thought.
His body had already lifted the boy's bandaged hand and brought it to his lips for a soft kiss before his mind had time to even realise what he was doing, let alone stop it. The blonde's mind went into overdrive as soon as it caught up. What had he just done? Backing away from the boy, he flushed and stuttered, noticing that the other was in a similar state.
"Sorry my boy, I got a little carried away. It's just an American thing. A way to comfort someone. I wish you a fast recovery." Toshinori explained, rambling excuses but still trying to sound calm and believable. Platonic kisses were more common in America than Japan after all. He just hoped that, being purely Japanese, Midoriya wouldn't know any different.
"Ah, ok. An American thing. I get it." The boy said, nodding his head in understanding.
They didn't mention it again.
The second time was after the students' fight with Stain and Midoriya's vast improvement with Gran Torino. All Might had known that Midoriya would learn a lot from his old mentor, but he was always amazed by just how fast the boy progressed. Looking back, he was sure he hadn't progressed that fast, it was Midoriya's will power. Toshinori thought absentmindedly that maybe his student was just special too. Even more than that was his ability to charm people; the blond wasn't sure he'd ever heard his old teacher praise anyone as much as he had praised Midoriya. It had been in the old man's own subtle way of course, but he understood the real meaning of the fond insults and criticisms.
He had called Midoriya to his office to finally tell him about All for One and the difficult and painful future he had fated the boy into, but he couldn't bring himself to take away that bright smile. The same bright smile that appeared whenever Midoriya saw All Might. The same one that made his whole day better. Exposing the young man to harsh reality could wait a little longer. Not thinking straight, he leaned forward and placed a gentle kiss on Midoriya's forehead beneath his untameable hair.
"Sorry." He muttered.
"Don't worry, it's just an American thing, right?" Midoriya said cheerfully, despite his smile being more forced than before.
"Right. Just an American thing." Toshinori told himself in agreement as his student left the room, his head in his hands thinking he'd just done something incredibly stupid, again, and he couldn't claim it was completely an accident this time.
The third time he had difficulty explaining to himself. There had been no high stress situation leading up to it nor had Midoriya been upset at all. He had been proud of the boy – he was always proud of his student – but only the usual amount. He couldn't brush it off as an accident this time. He had known full well what he was doing.
It had been an ordinary meeting, just like so many others they'd had before, sitting in All Might's office eating lunch together. It had been Izuku's idea originally, but he couldn't deny that it was now easily his favourite part of the day. They told each other about their day so far and talked about unimportant things, nothing special, but it was the simplicity of it, the mundane closeness that Toshinori loved so much. Although, he hadn't admitted that to himself yet, let alone the young man in question. His student still believed the hero was just humoring him as his successor and biggest fan, checking if he was bothering the man every day when entered the office, holding his bento box hopefully. Toshinori could never say no to him, no matter if he was flooded with work. He could never resist those eager green eyes.
Izuku was generally an enthusiastic eater – he had earned his hunger after a morning of classes and training - and the blond man had no doubt the boy's mother made delicious food, so it wasn't hugely unusual for a stray grain or two of rice to stick to his cheek. What was unusual was Toshinori walking around the desk, bending down and brushing them off. Even more unusual than that was the barely there kiss he left on the other's cheek before he sat back down on his side of the desk.
"Oh, that was that weird American thing again." Izuku realised aloud between mouthfuls of food. Unfazed, he continued eating until the bell declared it time to resume classes and they bid each other an ordinary goodbye until the next time they met.
After the fourth time, Toshinori could no longer avoid or deny, to himself at least, that he considered Izuku more than just a fan, successor or student. It was becoming increasingly obvious to him that he needed to seriously consider what his feelings were towards the young man.
He couldn't deny the fact that when standing behind the boy and fixing his stance during training, he had pressed a kiss to unruly hair, slight flattened and damp with sweat. He couldn't deny that the changes to the stance could have been just as easily explained with words.
He couldn't ignore that he had not even done it once, but twice. When his student got the stance correct, he planted another kiss on his head.
He couldn't deny the fact that he had done it all on purpose this time.
"Well done my boy!"
"You're doing that American thing again." Izuku announced.
"Sorry." He replied cheerfully, not really sorry at all.
Toshinori couldn't avoid that he was in love with Izuku, his own successor.
By the fifth time, Toshinori knew he was in love with his student. However, he also knew it would not be right to do anything about it. Not now. They needed to focus all their effort and time on preparing to fight All for One and for Izuku's rapidly approaching debut as a pro hero. They both knew that the hero All Might didn't have much longer. They couldn't let anything distract them; it was too dangerous.
Fighting Izuku for the final exam had pained him, the vice grip on his heart getting stronger with every injury he inflicted. Logically, he knew it was his job as mentor and U.A. teacher to test his student and to push his limits – this was for the sake of his future hero career and graduation from U.A. so he had to do it – but he couldn't ignore the pain it caused him. He had done his best not to go easy on the pair, using his full remaining power as All Might, and he had been practically glowing with pride when the young man had passed the practical exam, despite the challenging match-up and uncertain start.
Toshinori hoped it hadn't been too suspicious when he carried the two boys to Recovery Girl's tent and sat by Izuku's bedside, refusing to move. He also hoped no one saw him brush his student's bangs and aside and press a kiss to his forehead, lingering longer than he knew he should have. He knew he shouldn't have kissed him at all, but the boy was asleep. What harm could it do?
"Sorry my boy, it's just an American thing." He whispered quietly to the sleeping hero.
Even once Izuku had woken, All Might did not leave his side.
It wasn't until the fight with All for One that All Might realised just how hopelessly in love with Izuku he was. Despite the desperate situation he was in, he couldn't help worrying more about his student's safety than his own. He would have sacrificed himself without a second's hesitation if it had meant that Midoriya could escape. It was lucky he hadn't needed to of the battle could have ended very differently. Even in the worst parts of the battle, when he thought he really might die here, fighting All for One, all he could think of was Izuku Midoriya. The thought of seeing a smile light up the boy's face kept him going, kept him alive.
When they met on the beach that evening, Toshinori couldn't help himself. He hugged his student, lifted his chin and kissed him gently on the lips as the other cried.
"Is... Is this an… an American thing too?" Izuku sniffled.
"No my boy. This is an 'I love you' thing.' Toshinori replied with a smile.
A grin broke out on the other's face despite a few tears still falling down his cheeks.
"Good," he said as he leaned up and pressed a kiss of his own onto the blond man's lips, "because I don't want you to do that to anyone else."
The former pro hero grinned. "I won't," He let out a relieved sigh. "now that I don't have to hide it anymore."
They kissed again, neither quite sure who started it.
"I love you Izuku Midoriya."